Tweak hpi

Changes from pivotal:

I think the house price index graph needs to be at the bottom of the housing dashboard please? 

While we are at it I think we need to define our 100 index point in the sub head - so
Average HPIs by region
Becomes
Average HPIs by region (100 = February 2002)

Also while I'm at it, can the More Info say simply : "Source: Office of National Statistics (ONS)", ie as well as changing text remove the TBD bit please?